The fizzy drinks market, more particularly the market for the sparkling lemonades known as soft drinks or diet drinks, is steadily growing. From the industrial point of view, however, its development is coming up against the cost of transportation and of the relatively large number of handling operations associated with a heavy and bulky product. Attempts are currently being made to solve such problems by spreading the production centers as far apart as possible and only transporting concentrated extracts, in the dry or liquid state.
In the appropriate industrial plants, these extracts are treated with water, sugar, if necessary, and then CO.sub.2 under high pressure before being packaged in hermetically sealed containers which are pressure-resistant and hence relatively heavy and bulky. The "fizzy" quality of these drinks when consumed is then provided, inter alia, by the gradual release of the dose of CO.sub.2 initially dissolved therein.
Pulverulent dry extracts based on sodium bicarbonate and edible acids are also known which can be made into fizzy drinks by adding water just before consumption. However, the aeration of the drink which can be achieved with these extracts does not compare, in terms of its duration and its "fizziness", to that which results from the dissolution of CO.sub.2 under pressure. It is also found that, in numerous cases, the ingredients essential for the desired organoleptic effect, for example phosphoric and citric acids or sodium bicarbonate, are particularly hygroscopic and thereby impair the stability of the packaged mixtures.
The chemical and pharmaceutical industries produce and use polymers for coating drugs. Some of these polymers are suitable for protecting dry extracts from moisture uptake and for partially controlling the reaction between the acids and the carbonates. Not having been designed for this purpose, they have disadvantages such as coloring the froth or deposits in the glass. Moreover, their ability to control the release of CO.sub.2 from the drink and keep it uniform is far from perfect.
In the field of effervescent drinks more particularly, certain solutions have already been put forward. U.S. Pat. No. 2.868.646 recommends the use of water-soluble gums to coat crystalline mixtures of edible acids and bicarbonates, in the presence of high proportions of sugar. This method is unsuited to the use of phosphoric acid as well as to the preparation of so-called diet drinks which are low in calories.
U.S. Pat. No. 3.082.091 describes the use of vegetable gums, in particular guar gum, for coating the sodium bicarbonate. Although relatively stable in the dry state, the bicarbonate coated in this way does not enable a controlled release of gas once it has been brought into contact with water and acid. U.S. Pat. No. 3,667,962, which recommends the use of water-soluble porous matrices based essentially on dextrins, in which acids and carbonates are dispersed, is also unable to give the desired effects.
The most remarkable effects have so far been obtained using the coating method defined in European Patent Application No. A-0 130 144. The acid and carbonate constituents are each coated or impregnated with a liquor based on water-soluble macromolecular polysaccharides of vegetable origin, such as gum arabic and gum tragacanth. To obtain the desired properties, the solutions of macromolecular polysaccharides are first subjected to a moderate heat treatment in the presence of ethyl alcohol.